As DRAMs increase in memory cell density, there is a continuing challenge to maintain sufficiently high storage capacitance despite decreasing cell area. Additionally, there is a continuing goal to further decrease cell area. One principal way of increasing cell capacitance is through cell structure techniques. Such techniques include three-dimensional cell capacitors, such as trenched or stacked capacitors.
One type of capacitor structure forms at least one of the capacitor electrodes into a container-like shape. A suitable opening is formed within a container forming material, typically a dielectric layer although bulk and other substrate materials can be used. A conductive layer is formed within the openings to partially fill them to form upwardly open vessel-like structures. The conductive material is then patterned or planarized back, typically to form isolated capacitor electrodes for the capacitors being formed. Some or all of the container forming layer might then be etched from the substrate to expose outer sidewalls of the container-shaped electrodes. One or more suitable capacitor dielectric layers would then be formed over the container-shaped electrode. Another conductive layer is then formed over the capacitor dielectric layer(s) and patterned or otherwise processed to complete the capacitor construction.
As minimum feature dimensions get smaller and smaller, the thickness or vertical length/height of devices tends to increase, and does so particularly with capacitors in order to maintain adequate surface area and accordingly desired capacitance.